1. Field of the Invention
The invention relates to a method of producing structures for integrated semiconductor circuits and somewhat more particularly to a method of producing structures composed of photosensitive resists on substrates for semiconductor circuits, during the manufacture of which photolithographic processes are successively executed for producing masking structures without the intervention of a high temperature process.
2. Prior Art
Photolithographic steps are contained in the process sequence for manufacture of integrated circuits on silicon crystal wafers. During such manufacture, a photosensitive resist structure functions for masking and/or structuring the semiconductor surface. For example, a layer of a photosensitive resist which functions positively, can be applied to a silicon crystal wafer, coated over its entire surface with a silicon dioxide layer, and such resist layer can then be exposed and developed to form select structures, generally termed masks. A photosensitive resist mask generated in such a manner can either be employed in subsequent etching processes for structuring the silicon dioxide layer located therebelow or such mask can be used directly as a mask for doping substances to be implanted into the silicon crystal wafer.
In instances where two such photolithographic steps directly follow one another in a process sequence, then the adhesion of the second layer of photosensitive resist to the substrate surface (in the above discussion, to the oxide layer) can become so unsatisfactory, if no high temperature process intervenes, that the generated structure of photosensitive resist shifts or even comes-off during the development process or during rinsing after development.
In order to prevent such loosening or lifting-off of resist structures, the art presently completely removes the first generated resist mask, cleans the silicon wafer and thereafter tempers the wafer, for example, for one hour at, for example, 300.degree. C. in a nitrogen atmosphere and only then applies the second layer of photosensitive resist, after the application of an adhesion promoter. This second layer is then structured into a desired mask. Thus, a satisfactory adhesion of a second or subsequent photosensitive resist layer on a silicon crystal wafer provided with, for example, a silicon dioxide layer, is presently achievable by a thorough cleansing of the substrate surface, tempering and the application of an adhesion promoter.